The present invention relates to an agricultural tillage system. More particularly, it relates to a tillage system that is capable of working the soil at a shallow depth with discs, and also providing some deep (xe2x80x9cprimaryxe2x80x9d) tillage at a second, deeper depth, and then leveling the field, all in a single pass, thereby conserving fuel and equipment operating time.
Single-pass tillage implements providing both shallow and primary tillage in a single pass using discs and chisel points are disclosed in U.S. Pat. Nos. 4,245,706; 4,403,662; and 4,538,689. These machines, however, leave furrows and/or ridges in the soil after use. It has become desirable to leave the surface of the soil as level as possible after tilling in the Fall to reduce the amount of soil preparation necessary before planting the following Spring. U.S. Pat. No. 5,080,178 discloses a disc leveler for use with a tillage machine such as is disclosed in U.S. Pat. No. 4,403,662.
During the late 1970""s, before the machine shown in U.S. Pat. No. 4,403,662 became available, primary tillage was accomplished principally with moldboard plows. The moldboard plow leaves large slabs and chunks of soil that tend to break down over the freeze and thaw cycles of Winter, but this tillage practice required substantial working of the soil in the Spring in order to level the field and prepare it for planting of the next crop. Moreover, moldboard plowing is not an effective remedy for soil erosion, and has a tendency to exacerbate erosion.
In recent years, farmers have been looking for ways to decrease soil and wind erosion. The use of a large disc assembly in front of a chisel plow on a parabolic shank accomplished these goals and also breaks up the hard plow pan (or xe2x80x9csolexe2x80x9d) that is created at the particular depth at which the plow is set to operate, caused by repeated tillage at the same depth over the years. The parabolic shank and winged point of recent improved plows have reduced soil erosion, but this practice also may create large chunks of soil, and it usually requires substantial spring soil-working to prepare an adequate seedbed for planting.
During the 1970""s, the cutter chisel was widely used. It consisted of a chisel plow with a row of coulters to cut the residue ahead of two rows of staggered shanks on thirty-inch centers. These shanks had a four-inch twisted point attached to them to perform the primary tillage. The tip of the point was at approximately a 45xc2x0 angle to the horizontal, sloping downwardly and forwardly from the shank. The worked soil followed the curvature of the xe2x80x9cCxe2x80x9d-shaped shank that was attached to the chisel plow and was twisted in order to provide a moldboard-type turning action. A xe2x80x9cCxe2x80x9d-shaped shank, of the type described, is shown in U.S. Pat. No. 4,403,662.
For early cutter chisel plows, there was a net lateral movement of soil. A machine with, for example, 11 shanks would be equipped with five right-hand and six left-hand twisted points. The result was that a wide groove and a large berm were left after a pass. The machine as shown in U.S. Pat. No. 4,403,662 was an improvement because it left a smaller groove and not as large a berm by using fore and aft sets of discs and an improved point.
In U.S. Pat. No. 4,538,689, there is disclosed a winged point mounted on a parabolic shank. That winged point, in the combination shown, creates a large, rough surface similar to the surface of the moldboard plow used during the late 1970""s and early 1980""s. The wings on these points are set at a soil lift angle of approximately 30xc2x0. This lift angle was conventional at the time, but it is an aggressive angle which causes the wings to lift the soil abruptly. In some soils, particularly more compacted soils, the combination of an aggressive lift angle on the wings of the point, together with a parabolic shank, which is designed to lift and heave soil, lifted larger soil chunks and threw them out of the paths of the chisel plow and away from cooperating discs, making it difficult to create a level soil surface after a pass of the machine.
During the 1980""s, farmers desired less tillage to prepare for planting. The furrows left by the chisel shanks had to be filled with the berms that were created between each shank. In order to fill these furrows behind large parabolic shanks, smaller shanks were placed to run shallower and were placed midway between the large chisel shanks. This resulted in smaller grooves on reduced centers. With the development of the disc leveler shown in U.S. Pat. No. 5,080,178, the furrows behind the shanks were substantially filled without leaving substantial grooves after the shanks had passed, thus improving the levelness or xe2x80x9csmoothnessxe2x80x9d of the surface.
In heavily compacted soils, a parabolic shank lifts out large chunks of soil and heaves them to the path of least resistance around the shank. These large chunks are difficult to rearrange in such a way as to give a smooth resulting surface. If a chunk is rather large, it will tend to ride up the shank, roll forward and not be in the proper location for the leveler to roll it back to its original location, because the leveler primarily moves the soil laterally, not backward.
The present invention is directed to a tillage system, which is designed to perform complete tillage of the soil in a single pass while leaving a fairly level surface to reduce the amount of soil preparation required for planting the next season. Specifically, the present system cuts and buries residue, provides shallow tillage with discs, and provides a controlled amount of primary (deeper) tillage without creating a plow sole. As used herein, primary tillage means deep soil plowing, in a range of approximately nine to fourteen inches or greater. Shallow tillage may be in a range of three to six inches approximately. Finally, a leveler smooths the surface behind the chisel shanks.
The overall system functions are achieved through the cooperative action of widely spaced forward disc blades (sometimes referred to as the tillage discs to distinguish them from the trailing leveler discs) followed by chisel plows with winged points. Each plow point is located to the side of a strip of soil left untilled by the forward discs. The tillage discs are arranged in a forward set and a rear set with adjacent discs being offset in the direction of travel. One disc from the forward set and an associated one from the rear set cooperate to till adjacent swaths and move the soil (and residue if any) in opposing lateral directions. The tillage discs are arranged in cooperating pairs. A cooperating pair of tillage discs includes one disc from the forward set and one from the rear set with their working surfaces facing each other (i.e., in laterally xe2x80x9copposingxe2x80x9d relation). Adjacent sets of cooperating discs are spaced with one disc from the forward set and one disc from the rear set having their non-working surfaces spaced to leave a strip of untilled soil.
By running the tillage discs at an operating depth in the range of approximately three to six inches, large chunks capable of riding up the plow shank are avoided. Further, some of the tillage discs run nearly in-line ahead of the shanks. That is, the shanks are placed to run adjacent to the edges of the strips of untilled soil left by the tillage discs. The discs provide a notch effect, leaving a furrow fairly closely aligned with the shank. Thus, the disc cutting into the previously untilled soil creates a furrow and the trailing plow, with its point working at a deeper level, is located near the furrow created by a forward tillage disc, at the edge of an untilled strip. This relationship permits the plow more easily to break through the compacted soil with less energy imparted to the soil, reducing a tendency to create large clumps of soil.
The action of the tillage discs is characterized by an aggressive tilling of the soil and top residue. By aggressive action, it is meant that each tillage disc on the forward set is placed at an operating depth, working angle, and lateral spacing from an associated disc such that its leading edge cuts the residue and the disc blade scoops or shovels the soil and residue at a comparatively shallow depth (typically in the range of three to six inches) by turning the soil over, mixing the residue and soil and displacing the mixture laterally in a windrow at least partially covering the swath to be worked by a cooperating disc on the rear set. A cooperating disc from the rear set of tillage discs then tills a swath spaced laterally from the cooperating forward disc, cuts into compacted soil, mixes it with the windrowed soil from the forward cooperating disc and moves the mixture in the opposite lateral direction from its associated forward disc and at least partially behind the forward cooperating disc.
As mentioned, the pairs of cooperating discs are spaced laterally apart to leave a swath of untilled soil. That is, the non-working surfaces of a forward disc in one cooperating pair is spaced laterally from the non-working surface of the nearest disc of the adjacent cooperating pair to leave an untilled strip, which may contain soil and residue worked by the tillage discs.
Located behind the tillage discs in the untilled strips, are chisel plows with winged plow points set at a xe2x80x9cdeepxe2x80x9d or primary operating depth in the range of nine to fourteen inches. They are located to till the untilled swaths left by the tillage discs.
During the past decades, tillage speeds have increased. Speeds above 5xc2xdmph, especially, can roll large clods out of the shank path. According to the present invention, the wings on the point are shaped so that the soil has a longer path as it is lifted, and the lift angle is less than 30xc2x0 relative to the horizontal. The lift on the inner portions of the wings is greater than on the outer portions. That is, the soil path is longer adjacent the central tooth, and provides the twisting and mixing action of the soil. This allows the rear disc leveler effectively and easily to smooth out the surface of the tilled, mixed residue and soil. It is desirable to put some twisting or moldboard-type of roll to the soil in order to mix and bury surface-applied fertilizer and residue deeper into the soil.
The greater lift of the inner portion of the wings and the moderated lift of the outboard portions produces an outboard roll to the soil without lifting and hurling large chunks as far vertically or forwardly. That is, the principal movement of the soil tilled at the primary level is to the side, not forward This helps to prevent the soil from rolling forward and leaves the field with a more even surface in a fore-and-aft direction.
The chisel shanks carrying the plow points are located in the untilled strips of soil between adjacent pairs of cooperating discs. Specifically, the shanks are located toward the lateral edge of an untilled strip left by the tillage discs. This places the point adjacent the location at which a disc has formed a shallow furrow. Thus, the vertical distance between the tip of the point (which performs the primary or deep tillage) and the bottom of the furrow of secondary or shallow tillage is at a minimumxe2x80x94of the order of four to ten inches typically. The churning, lifting action of the plow point is muted by this reduced fracture distance (called the xe2x80x9cline of weaknessxe2x80x9d or xe2x80x9cfracture linexe2x80x9d) because it takes less force or energy to break the soil along a shortened line of weakness so less energy is imparted to the fracturing soil; and the broken soil is less likely to move any substantial distance, either laterally or forward. This cooperative action along the line of weakness leaves a more even surface profile after the chisels pass. The profile between adjacent chisels after they pass is a slight mound, the top of which is approximately centered between adjacent chisels.
A small optional shark fin can be attached to the top of the point. Such fins have been used for many years to help part the soil.
Leveling discs may be placed behind the chisels. The levelers are also arranged in pairs of discs with their non-working surfaces opposing each other. Each pair is centered on the ridge of the berm created by the chisel plows. The leveler discs of adjacent pairs thus part the berm and spread the soil laterally behind the chisel plows to create a smooth or level final surface profile of loosened soil (some of which has been deep-tilled), residue and fertilizer (if fertilizer had been applied before the tillage implement passed). The leveler disc blades as shown in U.S. Pat. No. 5,080,178 are approximately at a 15xc2x0 angle. When mounted to help smooth the field in the instant invention, it has been found that it is best to run the blades at approximately a 25xc2x0 angle. That is, the axis of rotation of the disc makes an angle of 25xc2x0 relative to a line perpendicular to the direction of travel.